In metaphasc plates of somatic divisions in root tips 36 chromosomes were found. 4. In some cultivated clones of Hevea brasiliensis showing partial or total male sterility, irregular meiosis takes place which is coupled with the occurrence of univalents and multivalents; of the latter trivalents are most common. The same irregularities were found in the hybrid of H. Spruceana X brasiliensis. 5. A case of asynapsis in a clone of H. brasiliensis, showing complete female and male sterility, has been described and compared with asynaptic meiosis in other plants.